Control circuits



Feb. 22, 1949.

J. E. YOUNG ET AL 2,462,799

CONTROL CIRCUITS Filed March 21, 1945 I {0 cl A um- RAISE/W7??? i O Q 70A/vmv/vA L 1 so cyc Ls SUPPLY IN VEN TORS .10 H N LYU u NE AND WILLIAMEM EUWN HTTOFNFY Patented Feb. 22, 1949 CONTROL CIRCUITS John E. Young,Merchantville, and William E. McCown, Gloucester, N. 1., assignors toRadio Corporation of America, a corporation of Delaware ApplicationMarch 21, 1945, Serial No. 584,020

5 Claims. 1

This application involves control circuits for turning oif orinterrupting the operation of amplifiers, relays, or generators of waveenerg such as transmitters of any type, whose output includes continuoussubstantially steady carrier energy, in the event of a decrease orinterruption of said output. My invention is especially applicable totelephony transmitters of the frequency modulation, amplitudemodulation, or phase modulation type.

The general broad object of my invention is improved control of waveenergy enerators, amplifiers, relays, or transmitters.

A more specific object of m invention is to provide an indication, or toshut down a transmitter or other source of wave energ upon any change inthe character of the load at the transmitter or source output, such aswould result from arc-over or other failure in the transmitter circuits.

In the prior art circuit controls operating on a change of voltage insome part of the circuit are known. Likewise, circuit controls operatingon a change in the magnitude of current in some part of the circuit areknown. Neither of these known types of control are entirely satisfactorybecause in the systems operating on voltage change there may be acircuit failure that still permits voltage of the normal operatingamplitude to be developed at the monitoring point, and the control isnot operated to break the circuit or perform other protective operationsto prevent damage to the circuit. Likewise, in the systems operating oncurrent change there may be circuit failures which do not result in amaterial current intensity change which in turn may be used to operatethe control circuits.

Take for example a known arrangement wherein a transmitter feeds a loadover a line and the control voltage is picked up from the line. Anarc-over in the line may occur due to defective insulation. If thisarc-over happens at a certain critical fraction of a wave length or amultiple of said fraction from the monitoring point, that is, the pointfrom which the control circuit exciting voltage is derived, the voltageat that point may not change in magnitude. Then the control circuitwould not be excited to function as intended. Likewise, if the failuretakes place at a critical distance from the point at which themonitoring current is obtained there may not be a change in theintensity of the current and again the control would not be actuated toshut down the transmitter or otherwise condition the same so that damagewill not result from the said circuit failure.

An object of our invention is to provide a radio frequency circuitcontrol system that is free of the above and other defects.

In systems of the type mentioned above by way of example, practicallyall circuit failures cause a change in the ratio of the voltage to thecurrent in the load or line or transmitter output. In attaining theobjects of our invention as outlined above, we provide a control circuitwhich responds to this change that takes place in the ratio of thevoltage to the current at some point in the line between the load andtransmitter or other controlled circuit in the event of failure i thecircuit.

In describing our invention in detail, reference will be made to theattached drawings wherein the single figure illustrates by wiringdiagram and schematically the essential features of a transmitter orother radio frequency circuit control system arranged in accordance withour invention. In the drawings, l0 represents a transmitter or othersource of wave energy of any type having in its output steady carriercurrent or energy. The transmitter supplies output by way of a line l2to an antenna or other load circuit IS. The output circuits and load aregiven merely by way of example, and may take various forms to suit theneeds of the installation being controlled. In the sake of simplicityand to expedite description, a simple output line and an antenna feedline have been shown. The transmitter may include a disabling circuitwhich itself operates to shut down the transmitter, or the disablingcircuit may operate through other circuits to accomplish the controldesired. The controlled circuit is shown at 18 as comprising a pair ofleads connected to the transmitter for control purposes and to contacts26 to which operating current may be applied to excite the controlcircuit. As an example, the points 26 may be in the alternating currentsupply circuit for the rectifier system supplying the plate directcurrent potentials for the transmitter. On the other hand, the circuitI8 may be of a relay con trolling contacts in a circuit in thetransmitter directly or through other relays. One of the leads includesa contact operated by an armature 22 in a relay including winding 26,which is excited when the transmitter is operating properly to completethe circuit 16 to keep the transmitter in operation.

A first diode V! is connected by a condenser Ci between a point on theinner conductor of the line l2 and ground. The voltage supplied throughCI to the rectifier VI is propor tional to the voltage on the line.Rectified current flows through the rectifier VI to produce across theresistance PM a potential depending upon the magnitude of the voltagesupplied by CI. The line also includes an inductance LI coupled to aninductance L2 connected in series with the rectifier V2 and a secondresistance R2 wherein is produced a potential drop proportional to thevoltage induced into inductance L2. The

voltage induced in LZis proportional tothe current in the innerconductor of the transmission line 12 at point A. The rectifier V2provides current in the resistance R2 to set up thereacross a potentialdrop proportional to the voltage on V2 which is in turn proportional tothe current in the inner conductor of line l2. Apoint B on resistance RIis connected toone'cornerof. a rectifier bridge circuit 28, whilea-point C on. resistance R2 is connected to the opposed corner of thebridge rectifier. In effect, one diagonal of the bridge rectifier istapped across resistances RI and R2. The other corners of the bridgerectifier are connected respectively one, D, to the gridfifl of anelectron discharge tube V3, and the other, E, to a point on 'apotentiometer resistance R3in shunt to a portion of the secondarywinding of a transformer TI. Resistor R4 is also connected betweenpoints D and E so that it is in.

shunt to the input impedance of tube V3. A point on the transformer Tiis connected to the cathode 24'of tube V3 so that an adjustable amountof the secondary winding of the transformer Ti may be included in thegrid circuit of the tube V3. The transformer Tl has a primary winding iwhich may be supplied'by alternatingcurrent power such as, for example,60 cycle current at 110 volts; completed through the winding 26 and apart of thesecondary' winding of the transformer TI.

The tube V3 is a Thyratron oi the type known as 'a negative gridThyratron. In this type" of Thyratron'negative potential is applied tothe grid to prevent it from firing but if positive potential is. appliedto the anode the tub'e'fires as the negative'grid potential is decreasedbut before the'gridpotential becomes zeroor positive. In the embodimentillustrated we apply the 60 cycle alternatingpotential to the grid andanode inphase opposition. The amount of alternating potential on thegrid is so adjusted relative to the alternating'potential on the anodethat when no negative bias potential is applied to the control grid frompoints D and E of rectifier :28 r

the tube will just draw enough current to excite relay winding 26'tohold armature 22 in the contactclosed position. It will be understoodthat an alternating potential is used'to critically bias the grid of theThyratron in lieu'of a direct current bias merely for the sake ofconvenience and simplicity. Since the alternating potentials applied tothe grid and plate from the alternat ingcurrent, source are inphaseopposition; the efie'ct is substantially the same as if a directcurrent bias were used; The tap on potentiometer R3 'isso adjusted thattheugrid of tube V3 is not biased to cutoff "and the tube is just'firingwhen the transmitter is operating. normally.

Then the points B and C on potentiometer re-' sistances RI and R'Zareadjusted so that the the other proportional to the current at the-sameThe point are rectified by tubes V! and V2. potentiometersRl'and R2 areadjusted so that no potentialexists between the points B and C undernormal operating conditions in transmitter Ill? The potentiometer'R3isadjusted so thatthe The anode circuit of the tube V3 is 60 voltagessupplied from points Band C tothe corners of the. bridge are just equal,there is no Thyratron V3 is biased near cutoff but still drawing enoughcurrent to operate the control relay 26. The rectifier bridge 28 isconnected 'so that any potential appearing between points B and C causespoint D to become negative with respect to E. This will be so since ifpoint C becomes positive current flows through the rectifier. 2! topoint E through R3 to the cathode 2 3; and to grid 30, to point D, andthrough rectifier 23 to point B. If point C becomes negative withrespect to point B current flows from point B through rectifier 25 topoint E, through R3 to cathode 2 to grid 36 to point D, and throughrectifier 2? to point C. The grid 36 then becomes more negative and cutsoff the current through winding 26 to permit contact 22 to open andinterrupt the circuit l8 to stop operation of the transmitter.

V2 will change and the potentials thereby developed at points B and Cwill become unequal and increase the negative bias on the Thyratron grid33, causing the relay contacts includingZZ to open to operate throughcircuit !8 or circuits controlled thereby to shut down the transmitter.

As soon as the control circuit has functioned to I shut down thetransmitter, the potential from B-to C returns to zero, the Thyratronfires, and the relay contacts are reclosed, thereby restoring thecircuit to normal. arranged to then restart automatically or under thecontrol of the operator.

What is claimed is:

1. In electrical apparatus for controlling the operativeness of a radioor equivalent circuit wherein continuous alternating currentappearsduring operation, a rectifier for deriving a voltage themagnitude of which depends on the voltage in said circuit, a secondrectifier for de-' riving a voltage the magnitude of which depends onthe intensity of the current in said circuit, a bridge circuit connectedto said recifiers for comparing said derived voltages, and a tubecoupled to bridge circuit and subjected to changes in derived voitagesfor controlling the operativeness of said circuit in the same sense bychanges in either direction in the either of the compared voltages.

2. In apparatus for controlling the operativeness of a radio orequivalent circuit in accordance with changes in magnitude of continuousalter nating current, a rectifier and a resistance for deriving avoltage the magnitude of which 'depends on the voltage in said circuit,a second rectifier and a second resistance for deriving a voltage themagnitude of which depends on the intensity of the current in saidcircuit, abridge circuit having four impedance arms, connections betweenopposed corners of said bridge and said resistances, atube having acontrol "grid and a cathode coupled to other points on said bridge, anda relay associated'with said first mentioned circuit and coupled to theoutput electrodes-of the tube.

3. In combination, a transmitter, a load coupled to said transmitter bya transmission line, a control circuit including contacts for saidtransmitter, a first rectifier circuit coupled by a condenser to a pointon said line to be excited by the voltage I therein, a resistance insaid first rectifier circuit, an inductance in said line, a secondinductance coupled to said first inductance and connected in a secondrectifier circuit including a second resistance, a gaseous tube'havingananode coupled Thus if either the reactanceor resistance of the load l2,l6, etc, changes the ratio of the potentials applied to tubes V8 and Thetransmitter may be magnitudes of to a relay winding associated with saidcontacts, said gaseous tube having a control grid, a bridge circuithaving a first diagonal connected between the control grid and cathodeof said gaseous tube, said bridge circuit having a second diagonal, andconnections between the second diagonal of said bridge circuit andpoints on said resistances.

4. In combination, a transmitter, a load coupled to said transmitter bya transmission line, a control circuit including contacts for saidtransmitter, a first rectifier circuit, including a load impedance,coupled to said line to produce voltage of a magnitude depending on themagnitude of the voltage in the line, a second rectifier circuit,including a load impedance, coupled to said line for developing avoltage of a magnitude depending on the intensity of the current in saidline, a gaseous discharge tube having an anode coupled to a relaywinding associated with said contacts, said tube having a control gridand a cathode, a bridge circuit having a first diagonal connectedbetween the control grid and cathode of said tube, said bridge having asecond diagonal, and connections between the second diagonal of saidbridge and said load impedances.

5. In combination, a source of wave energy of substantially steadyconstant strength, a circuit excited by said energy, a first rectifierexcited by voltage at a selected point in said circuit, a secondrectifier inductively coupled to said circuit at said point, an electrondischarge device having a control grid and having in its output a relaywith contacts in said circuit, a circuit for applying a biasingpotential to said grid of a value such that said tube is conductive, aload impedance for each rectifier, and a circuit coupling said loadimpedances to said control grid of the device to apply to said controlgrid a less positive bias to reduce the conductivity of the device inthe presence of material changes in the intensities of the currents insaid rectifiers.

JOHN E. YOUNG. WILLIAM E. MCCOWN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

